Benchmark: timing 1500000 iterations of Concatenate, Interpolate, Substr...
Concatenate:  1 wallclock secs ( 1.56 usr +  0.00 sys =  1.56 CPU) @ 960000.00/s (n=1500000)
Interpolate:  1 wallclock secs ( 1.59 usr +  0.00 sys =  1.59 CPU) @ 945812.81/s (n=1500000)
    Substr:  2 wallclock secs ( 2.07 usr +  0.01 sys =  2.08 CPU) @ 721804.51/s (n=1500000)